Manufacture of soap



Patented Nav. 3o, 1943 MANUFACTURE F SOAP Leopold Sender, Baltimore, Md., assignor to The Shan-ples Corporation poration of Delaware Philadelphia, Pa., a cor- Applioation March 6, 1942, Serial No. 433,589 4 Claims. (Cl. 252-489) The present invention relates to the art of soap making, and was conceived `as an improvement in recently developed methods of making soap continuously with the aid of centrifugal separators. Processes for the manufacture of soap by passing a saponifying reagent continuously into confluence with a source of fat, saponifying the fat by passage of the mixture at saponifying temperature continuously through mixing apparatus, and separating spentreagent from fat by centrifugation are described and claimed in the patents to Ashton T. Scott, Nos. 2,300,749 and 2,300,750. The present invention constitutes an improvement over the procedure of the two Scott patents referred to above resulting in improved rate of utilization of the saponifying reagent in saponiflcation of the fat.

In the processes of the above-mentioned patents of Ashton T. Scott, the fat is continuously saponied by treatment with a saponifying reagent such as lye, the saponiiication being accomplished by intensely mixing the fat and lye while passing them at a saponifying temperature through closedimixing apparatus under superatmospheric pressure. The resulting soap-containing mass is maintained under intensive agltation practically up to the moment when it is passed into a centrifugal separator for removing the aqueous reagent phase from the soap. The saponiflcation is preferably accomplished in a plurality of counter-current stages, and the removal of the soap from the zone of centrifugation is accomplished by mixing water or saponifying reagent with the soap while it is still in a turbulent condition due to discharge from the zone of centrifugation. The soap is grained, and

thus conditioned for removal of the aqueous phase, prior to centrifugation, by the addition of a salt solution, or an excess of saponifying reagent which serves as a salting out agent. "In the process of Patent 2,300,750, the saltingv out operation is accomplished simultaneously with the saponiflcation by addition of thel salting 'out agent before the start o1' the saponication reaction.

At the conclusion of the nal saponiflcation step of the above-mentioned Scott patents, the soap from the centrifugal ofthe last saponification stage is mixed with water, and also with electrolyte if necessary, to change the grained or curd soap to a neat soap and at the same time form a new phase which is known as nigre. The neat soap and nigre are thereafter separated from each other by centrifugation.

The process of the present invention may be practiced in connection with operations o! either i ofthe types discussed in the above-mentioned Scott patents; i, e., either in cases-in which the salting out agent is present throughout the The processes of the'above-mentioned Scott patents have very substantial advantages over the prior art kettle process, as discussed in those patents, but there is some difdculty in obtaining eflicient utilization of the saponiiying reagent. In the performance of the first saponifying stage, it is desirable that the reagent employed for saponication be substantially completely utilized in the saponication reaction. In an ei'l'ort to accomplish this result, it is customary to use a quantity of saponifylng reagent in this step which is less than a molecular equivalent of the fat to be saponifled with the object of causing the reagent to be almost entirely used up. in saponiflcation of fat and discharging an aqueous reagent phase containing a minimum of liree saponifying reagent, while discharging grained soap containing at least a small proportion of unsaponifled fat from this iirst stage. saponifled fat contained in the grained soap is then saponifed in asecond stage by treatment with a further quantity of saponifying reagent added in this second stage. The object of this operation is to discharge from the second stage centrifugal a soap containing substantially no unsaponied fat. and to discharge' an aqueous reagent phase from this second stage centrifugal containing saponifying reagent not yet completely utilized in saponiflcation of fat. The aqueous phase discharged from the second stage centrifugal is then returned to the first saponiflcation stage and the free saponifying reagent contained in that phase serves to saponify further fat in the first stage of the process. More than two stages may. of course, be employed'in the saponification operations, but the general principle remains 'the same in any case, the object being to deliver a substantially completely grained soap-containing mass from the centrifugal ofthe last stage, while delivering a completely spent reagent as the aqueous phase from the centrifugal of the rst stage.

While-the attainment of the results of completing the utilization of the saponifying reagent in the first stage, and discharging from that stage The unan aqueous phase having substantially no further saponifying reagent value appears in theory to be achievable without serious difficulty, certain fac.- tors of the operation tend to defeat this result, and the attempt to practice the process by rapid continuougsaponiilcation imposes certain additional dimculty. Thus, while the use of a stoichiometric excess of fat in the first stage would appear in theory to accomplish the desired resuit, the saponifying reagent becomes progressively weaker by reason of the fact that it is being constantly used up in the saponification of fat and by dilution with-water of reaction.- Furthermore, every source of fat, regardless of whether it consists of a mixture of fats derived from different sources, includes fats which are chemically different from each other, and a portion of the fat used in the saponiflcation reaction is always more difilcult to saponify than another portion. As a consequence of this factV tinuous passage through the heated mixing and saponifying apparatus.

In accordance with the invention, the fat to be saponified in the stage in which it is desired that the saponifylng reagent be substantially completely utilized (rst, or killing change) is added in successive increments, a. portion of the fat being added at the beginning of the saponication reaction, and one or more additional portions being added during the course of the saponification reaction. or after that reaction has decreased materially in speed, or practically come to a stop. In one embodiment of the invention, the fat. added at an advanced point i'n this stage is a more reactive fat than that with which the saponifying reagent is mixed previously; i. e., before the beginning of the saponiilcation reaction. In any case, the fat added at an interme-A diate point in the passage of the initially added mixture through the mixer will be more reactive than that remaining in the mixture, after saponincation has commenced, even though the subsequently added fat be identical with that originally added, for the originally added fat will contain a smaller ratio of its more reactive to its less reactive constituents, even after saponiilcation has proceeded to only a slight extent. It will thus be seen that the crux of the invention consists in adding, at an intermediate stage of the reaction, a source offat which is more reactive than the fat remaining unreacted in the mixer,

and this greater reactivity of the subsequently,

added source oi' fat may be due to the fact that it has a higher reaction rate with the saponifying reagent than that of the fat which was initially added, or to the fact that the rate of reaction between the initially added fat and the saponifying reagent has been reduced by conversion of at least a part of the more saponifiable constituents of the initially added fat into soap. It will thus be seen that the subsequently added fat will be more reactive than the unreacted fat remaining in the mixture, even in cases in which the subsequently added fat is identical with the initially added fat.

The invention will be better understood by reference to the following detailed description in connection with the attached flow sheet, in which,

Figure l illustrates the practice of the invention in continuous saponiflcation of fat in a centrifugal soap manufacturing process, and- Figure 2 illustrates a stage of a soap manufacturing process involving use of an alternative form of the invention.

In the practice of the invention as illustrated in Figure 1, lye may be continuously passed to a mixer I2, which is preferably of the multi-stage type, this lye passing from container I0 into confluence with a flowing stream of fat from container II, and the two streams passing together into the mixer I2. The materials -fed to the mixer I2 are heated toa temperature sufilciently high to cause rapid saponiilcation of the fat (e. g., 200 F.) A further quantity of fat is mixed with the partially saponied mass in the mixer I2, at least a part of this fat being preferably added at a vzone of this mixer near the exit end thereof. In addition to introduction of a portion of the fat to be saponified at a zone of the mixer where the reagent has become considerably diluted and the more readily saponiilable fat substantially completely saponifled, as indicated by the arrow I'I, a portion of the fat may be added at an intermediate stage of the mixer as indicated by the arrow I8. Thus, as the saponilying reagent becomes weaker, and the fat introduced at the beginning of the saponiiication reaction becomes poorer in readily saponifiable constituents,

.fresh fat is introduced into the mixture in order to utilize the remaining saponifying reagent. By operating in this manner, the saponifyng reagent introduced into the first stage of the process may be used up rapidly in saponifying fat, there" by making it possible to use smaller mixing equipment for a given rate of throughput.

The saponifled mass of the first stage may be grained by addition of a salting out agent prior to the saponlilcation reaction, or the salting out agent may be added at a later portion of this stage. In any case, the mixture of grained soap and aqueous phase resulting from saponiflcation and graining in the mixer I2 is passed to a centrifugal I3, where the aqueous phase designated as spent lye is' continuously discharged in liquid balance against the grained soap-containing phase, which also contains some unsaponified fat. This grained soap phase is then mixed with a further quantity of saponifying reagent (lye) from container I4, as taught in the patents of Ashton T. Scott referred to above, and the resulting mixture is subjected to saponiilcation and graining in mixer I5 and separation into aqueous reagent and soap phases, respectively, in centrifugal I6, the aqueous saponifying reagent phase discharged from this centrifugal (partly spent lye) being returned to the first stage ofthe saponification reaction in order to utilize the restruction and function. A further quantity of fat B, of a more readily saponiable nature than the fat in container 2l, is introduced from container 22 into the partially saponified mass at an intermediate point of the mixer 25. A still further quantity of fat C, which is even more readily saponifiable than fats A and B introduced from containers 2| and 22, respectively, may be introduced from container 23 at a very advanced stage. of the mixer. By successively introducing fats which are more reactive with the saponifying reagent as the saponication proceeds, the disadvantages due to progressive dilution of the saponifying reagent and rapidity of the process are largely obviated, and an aqueous reagent phase (spent lye), containing very little saponifying reagent value, can be discharged from the centrifugal 24 with a considerably shorter time of contact than would otherwise be necessary.

In cases in which reference has been made to fats in the above discussion, it is to be underlstood that this term is intended to include the various sources of fats and acids which are reacted with bases to produce soap in conventional soap making operations. Thus, in the practice of the invention as illustrated in Figure 2 of the ow sheet, fat' A may be tallow, fat B may be cocoanut oil, and fat C may be a mixture vof fatty acids. l

Various modifications are possible Within the scope of the invention, and I do not therefore wish to be limited except by the scope of the following claims. When the term source of fat is used in these claims, this term is used to designate any substance containing fat or fatty acid to be used in the soap-making operation.

I claim:

1. In the manufacture of soap, a process comprising mixing a saponifying reagent with a source of fat, passing the resulting mixture continuously to a zone of centrifugation while mixing the saponifying reagent with the fat and maintaining the mixture at a saponifying temperature, and adding a further quantity of a more reactive source of fat than that remaining in said mixture and mixing said further quantity of source of fat with the mixture passing to the centrifugal separator, while said mixture still contains unreacted saponifying reagent, after saponication of at least a part of the initially mixed quantity of fat during said continuous passage to the centrifugal separator.

2. In the manufacture of soap, a process comprising mixing a saponifying reagent with a source of fat, passing the resulting mixture continuously to a zone of centrifugation While mixing the saponifying reagent with the fat and maintaining the mixture at a saponifying temperature, and adding successive increments of further quantities of more reactive fat than that remaining in said mixture and mixing said suc'- cessive increments of fatwith the mixture passing to the centrifugal separator, while said mixture still contains unreacted saponifying reagent, as the saponification reaction proceeds during said continuous passage to the centrifugal separator.

3. In the manufacture of soap, a process com prising mixing a saponifying reagent with a source of fat, passing the resulting mixture continuously to a zone of centrifugation while mixing the saponifying reagent with the fat and maintaining the mixture ata saponifying temperature, and adding successive increments of further quantities of more readily saponiiiable fat than said first-mentioned source of fat and mixing said successive increments of fat with the mixture passing to the centrifugal separator, While said mixture still contains unreacted saponifying reagent as the saponicatin reaction proceeds during said continuous passage to the centrifugal separator. l

4. In the manufacture of soap, a process comprising mixing a saponify ng reagent with a source of fat, passing the r/sulting mixture continuously to a zone of centrifugation while mixing the saponifying reagent with the fat and maintaining the mixture at a saponifying temperature, and adding a further quantity of a more readily saponiable source of fat and mixing said further quantity 0f source of fat with the mixture passing to the centrifugal separator, While said mixture still contains unreacted saponifying reagent, after saponication of at least a part of the initially mixed quantity of fat during said continuous passage to the centrifugal separator.

LEOPOLD SENDER. 

